wirelessing back the range, and French shells were falling very near the big guns.
The heavy guns, in modern warfare, are placed miles away from the objects they wish to hit, and the only way to know where the targets are is by aeroplane observation. When the guns are ready to fire one of the artillery control planes goes up over the enemy's territory. Of course it is the object of the enemy to drive it away if possible.
But, hovering in the air, the observer in the double-motored machine notes the effect of the first shot from his side's cannon. If it goes beyond the mark he so signals by wireless. If it falls short he sends another signal. Thus the range is corrected, and finally he sees that the big shells are landing just where they are needed to destroy a battery, or whatever is the object aimed at. The observation complete, the machine goes back over its own lines—if the Germans let it.
This sort of work was going on below them while Tom, Jack and the others in the Nieuports were engaging in mortal combat with the Hun fliers. Some of the heavy French shells fell beyond the emplacements of the big guns, and others were short. The observers quickly made corrections by wireless for the gunners. Tom Raymond, after a desperate swoop at his antag-
